Novel blowing agent for polymeric foam process

ABSTRACT

A process is disclosed for a polymeric foam such as a polyurethane foam prepared from a reaction mixture comprising an organic polyisocyanate compound and a compound having more than one active hydrogen, wherein the blowing agent comprises a mixture of ethanol and dibutylphthalate. The molar ratio of ethanol to dibutylphthalate is preferably in the range of from about 1.5 to about 4.

This is a division of application Ser. No. 882,280 filed Mar. 1, 1978and now abandoned.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention is broadly related to the field of polyurethanechemistry. More particularly, the invention relates to a process formanufacturing a foamed polymeric material from starting materials whichinclude a bitumen such as an asphalt and a hydroxy fatty oil such ascaster oil.

B. Description of the Prior Art

The term "polyurethane foam" is generally applied to foamed polymericmaterials in which the polymer contains significant numbers of urethanegroups, which have the characteristic structure ##STR1## whether theurethane group repeats regularly throughout the macromolecule or not.

Polyurethane foams are ordinarily prepared by the reaction of apolyisocyanate compound with compounds having two or more "activehydrogens." Such active-hydrogen compounds include polyhydroxycompounds, generally termed polyols, and compounds containing aminogroups or carboxyl groups. The active-hydrogen compound can containfunctional groups in addition to groups which supply replaceablehydrogens. For example, hydroxyl-terminated polyethers and polyestershave been widely used to prepare polyurethane foams. Castor oil andother hydroxy fatty oils have also been used as active-hydrogencompounds in the production of polyurethane foams, particularly rigidand semi-rigid foams. Suitable catalysts are often included in thereaction mixture in order to speed the polymerization reaction, althoughthe addition of a catalyst is not required in all applications. Gas forproducing the foam is usually generated at least in part by adding waterto the reactants. The water reacts with the polyisocyanate to producecarbon dioxide for foaming. In addition, blowing agents such aslow-boiling halocarbons can be mixed with the reactants to produce gasfor foaming. Surfactants and other additives are frequently included inthe reaction mixture to regulate the size of the foam cells andotherwise influence the properties of the resulting foam.

Within the polyurethane foam family, it is possible to obtain a widerange of physical and chemical properties of the foam by appropriateselection of the specific raw materials and the reaction conditions. Adetailed discussion of prior-art polyurethane compositions may be foundin Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd ed.,(Interscience, 1970), vol. 21, pp. 56-106.

Attempts have been made to incorporate asphalts and tars intopolyurethane compositions by one means or another in order to reduce thecosts of the starting materials and to produce a polyurethane materialhaving properties suited for a particular application.

One such attempt is disclosed in U.S. Pat. No. 3,179,610. The '610patent discloses compositions obtained by blending certainpolyurethane-type prepolymers with a bituminous composition such asasphalt or tar. The polyurethane prepolymers are prepared by reacting amolar excess of a polyisocyanate with a compound containing a pluralityof hydroxy or carboxy groups which are reactive with isocyanate groups.Castor oil is given as an example of such a compound. By using a molarexcess of the polyisocyanate when preparing the polyurethane prepolymer,unreacted isocyanate groups are present for further reaction or curing.The prepolymer thus prepared is blended with a bituminous material atroom temperature or an elevated temperature, the weight of theprepolymer being from 5 percent to 25 percent of the total weight of theblend. The resulting blend can be foamed and cured in situ by addingwater in amounts to react with the prepolymer, liberating carbondioxide. The '610 patent discloses using the foamed compositions as ajoint filler and sealer. All of the applications for the compositionsdisclosed in the '610 patent involve bonding the composition to anothermaterial in some way.

U.S. Pat. No. 3,810,860 discloses a process for polymerizing crudepetroleum hydrocarbons which involves a two-component system. The firstcomponent includes a crude petroleum hydrocarbon and an arvlenediisocyanate miscible with the hydrocarbon, and the second componentincludes a crude petroleum hydrocarbon, a hydrogen donor miscible withthe hydrocarbon, and an organic acid miscible with the hydrocarbon.Among the hydrogen donors disclosed in the '860 patent are mixtures of atertiary amine and castor oil. According to the '860 patent, highlyasphaltic crude petroleum hydrocarbons are generally not compatible inthe second component, the component which would include castor oil wereit to be incorporated in the hydrogen donor.

I have invented a process for manufacturing a foamed polymeric materialand products related thereto which possess constellations of usefulproperties not found heretofore in the art.

SUMMARY OF THE INVENTION

The present invention relates to a process for manufacturing a polymericfoam which comprises the step of preparing an intermediate reactant byheating a mixture of a bitumen and a hydroxy fatty oil to a temperaturesubstantially above room temperature and maintaining the mixture at sucha temperature for a time sufficient to enable significant fractions ofthe bitumen and the hydroxy fatty oil to react. As used herein, the term"bitumen" refers to mixtures of hydrocarbons of natural or pyrogenousorigin; or combinations of both; which may be accompanied by theirnonmetallic derivatives; which may be gaseous, liquid, semisolid, orsolid; and which are completely soluble in carbon disulfide. Thisdefinition is based on the one adopted by the American Society forTesting and Materials in "Terms Relating to Materials for Roads andPavements, " ASTM Designation D 8-55 (Philadelphia, 1955). In preferredembodiments of the present invention, the bitumen employed is solid orsemisolid at room temperature, although at higher temperatures it mayexist in a liquid or gaseous state. A preferred hydroxy fatty oil iscastor oil.

The process further comprises the step of combining the intermediatereactant of the preceding paragraph with a polyhydroxy compound, apolyisocyanate, and a gas-generating agent to form a polymeric foam. Thegas-generating agent is ordinarily water and a blowing agent. Preferredpolyhydroxy compounds and polyisocyanates are discussed below. Aparticularly useful blowing agent includes a combination ofdibutylphthalate and ethanol.

The present invention also relates to products made by the processdescribed above, as well as to the intermediate reaction product betweena bitumen and a hydroxy fatty oil and to the dibutylphthalate-ethanolblowing agent.

Because one of the starting materials is a bitumen, the foamed polymerof the present invention can be produced relatively inexpensively ascompared with conventional polyurethane foams.

The polymeric foam of the present invention can be used in many of theconventional applications for thermosetting polyurethane foams. Forexample, it can be readily cast in a mold or applied as a coating to asurface. However, it also has properties which make it particularly wellsuited for certain applications for which conventional foamed polymersare less well suited or cannot be used at all.

Preferred foamed polymeric products of the present invention cure tomaterials which are strong and tough. As a consequence, the polymericmaterials can be used to fabricate articles which structurally must becapable of bearing heavy loads. For example, pallets for use inwarehousing and shipping can be made from a preferred foamed polymericmaterial of the present invention. The pallets are light, but strongenough to be hoisted about fully loaded with a fork-lift truck undertypical warehousing conditions.

One feature of preferred foamed polymeric materials of the presentinvention is that, even after they are fully cured, they are soluble inmolten asphalt. Thus shipping pallets for roofing tar made from suchmaterials can be conveniently disposed of at a job site by breaking upthe pallets and casting them into the molten asphalt in the asphaltkettles.

The foamed product of the present invention is an excellent thermalinsulator. Moreover, the material is relatively impermeable to watervapor and other gases as compared to typical polyurethane foams and thuscan be used to advantage as a thermal insulating material forrefrigerators and the like where water condensation within an insulatorcan be a problem.

Certain formulations of the foamed material of the present invention arerelatively inert with respect to water as compared to typicalpolyurethane foams and thus resist weathering. Such foams can be used toparticular advantage as construction materials in the marine industry;for example, as insulation or flotation material on board ships.

Conventional polyurethane foams tend to be highly flammable andconsequently expensive fire-retardant additives must often beincorporated in such foams. Foamed polymeric materials of the presentinvention, on the other hand, can be formulated so that the need for afire-retardant additive is greatly reduced or even eliminated altogetherfor certain applications. Foamed materials of the present inventionhaving a density in excess of about eight lb/ft³ tend to have relativelylow flammabilities.

Preferred foamed polymeric materials of the present invention aregenerally odor free and are resistant to attack by mildew, mold, fungus,and the like.

The products of the present invention are ordinarily black in color andare good absorbers of solar radiation. It is anticipated, for example,that the material will find wide use as an absorbent backing forsolar-powered water heaters.

Panels for use in constructing buildings can be fabricated by foaming apolymeric material of the present invention between two sheets offiber-glass reinforced resin or the like. The resulting sandwich-likepanels are light and strong and can be used, for example, as wall boardsor roofing panels in the construction of houses. Inexpensive pallets forshipping and warehousing can be made with the foamed polymeric materialreinforced with tar paper. It will be apparent to those skilled in theart that foamed polymeric products of the present invention can be usedto make other reinforced articles and materials.

BASIC PARAMETERS OF THE INVENTION

An intermediate product can be manufactured by heating a mixture of abitumen such as an asphalt and a hydroxy fatty oil such as castor oil toa reaction temperature substantially above room temperature, therebyinducing a thermal reaction between the two components. For typicalasphalts and castor oil, the temperature range will ordinarily bebetween about 140° C. and about 200° C., the preferred range beingbetween about 145° C. and about 155° C., although reaction temperaturesoutside of these ranges may be preferred for other starting materials.It will generally be preferred to employ from about 20 to about 100parts by weight of the hydroxy fatty oil for each 100 parts by weight ofthe bitumen. The mixture of hydroxy fatty oil and bitumen is maintainedat the reaction temperature for a time, typically an hour or more,sufficient to enable significant fractions of the bitumen and thehydroxy fatty oil to react.

If the reaction between the hydroxy fatty oil and the bitumen is carriedout under an atmosphere of pressurized air, the resulting intermediateproduct generally tends to require less polyisocyanate to produceacceptable foamed polymeric materials. For example, if the reactionbetween a typical asphalt and castor oil is carried out under anatmosphere of air at a pressure of from about 5 psi to about 10 psiabove standard atmospheric pressure, the quantity of polyisocyanate canbe reduced by up to roughly 40 percent. Exposure to an atmosphere ofpressurized air can also be carried out at a later stage in the processto similar beneficial effect, for example, after the intermediateproduct is mixed with a polyhydroxy compound. The effect of suchtreatments with pressurized air is most pronouned when a non-blownbitumen is used as a starting material.

The intermediate product thus obtained is combined with otheringredients to produce the desired foam product. Such ingredientsinclude a polyhydroxy compound, a polyisocyanate and a gas-generatingagent such as water and a blowing agent. Additional ingredients such ascatalysts, surfactants and plasticizers can be included if desired.

Virtually all of the polyhydroxy compounds employed in conventionalpolyurethane foam formulations and mixtures thereof, including bothpolyester polyols and polyether polyols, can be employed as thepolyhydroxy compound referred to in the preceding paragraph.Representative polyether polyols include poly (oxypropylene) glycols,poly (oxypropylene-b-oxyethylene) glycols (block copolymers), poly(oxypropylene) adducts of glycerol, poly (oxypropylene) adducts oftrimethylolpropane, poly (oxypropylene-b-oxyethylene) adduct oftrimethylolpropane, poly (oxypropylene) adducts of 1,2,6-hexanetriol,poly (oxypropylene) adducts of pentaerythritol, poly(oxypropylene-b-oxyethylene) adducts of ethylenediamine (blockcopolymers), and poly (oxypropylene) adducts of sucrose, methylgucosine,sorbitol. Representative polyester polyols include those prepared fromthe following monomers: adipic acid, phthalic anhydride, ethyleneglycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol,diethylene glycol, 1,2,6-hexanetriol, trimethylolpropane and1,1,1-trimethylolethane. Generally it will be preferred that thepolyhydroxy compounds have average molecular weights as calculated fromtheir hydroxyl numbers in the range of from about 300 to about 9,000,with molecular weights in excess of about 400 being particularlypreferred. As specific examples, poly (oxypropylene) polyols havinghydroxyl numbers in the range of from about 350 to about 800 aresuitable for certain preferred formulations of the foamed polymericmaterial of the present invention. Another polyhydroxy compound:N,N,N',N'-tetrakis (2-hydroxypropyl)-ethylenediamine, which iscommercially available under the trade name of "Quadrol" from BASFWyandotte Corporation, is suitable for a number of preferredformulations, as are "Niax Pentol ", which is commercially availablefrom the Union Carbide Corporation, and "Voranol", which is commericallyavailable from Dow Chemical Company.

Suitable polyisocyanates include virtually all of the polyisocyanatesemployed in conventional polyurethane foam formulations, includingaromatic, aliphatic and cycloaliphatic polyisocyanates. A representativelist of such polyisocyanates includes: 2,4-tolylene diisocyanate,(65:35) tolylene diisocyanate, (80:20) tolylene diisocyanate,4,4'-diphenylmethane diisocyanate, dianisidine diisocyanate, tolidinediisocyanate, hexamethylene diisocyanate, m-xylylene diisocyanate,phenyl isocyanate, p-chlorophenyl isocyanate, o-chlorophenyl isocyanate,m-chlorophenyl isocyanate, 3,4-dichlorophenyl isocyanate,2,5-dichlorophenyl isocyanate, methyl isocyanate, ethyl isocyanate,n-butyl isocyanate, n-propyl isocyanate and octadecyl isocyanate. Formany applications it will be preferable for reasons of economy to employcrude mixtures of polyisocyanates. For specific examples, polymethylenepolyphenylisocyanates available commercially under the trade names"PAPI" and "Mondur MR" from the Upjohn Company and the Mobay ChemicalCompany, respectively, are suitable for a number of preferredformulations of the present invention.

Although gas-generating agents which do not include water can be foundwhich produce acceptable foamed polymeric materials according to thepresent invention, such agents are invariably more expensive thancorresponding gas-generating agents which include water. For thisreason, it is preferred for the gas-generating agent to include water.Conventional blowing agents for polyurethane foam can be used toadvantage in preparing the foamed polymeric materials of the presentinvention. Although it is not necessary in every case to use a blowingagent in addition to water, the use of water alone as a gas-generatingagent tends to produce a material which is friable, which is undesirablefor most applications. Examples of conventional blowing agents are thelow-boiling liquids trichlorofluoromethane, dichlorodifluoromethane anddichloromethane (methylene chloride).

A novel blowing agent particularly suited for manufacturing the foamedpolymeric materials of the present invention, as well as conventionalpolyurethane foams, comprises the combination of ethanol anddibutylphthalate. To prepare preferred formulations of the blowingagent, quantities of ethanol and dibutylphthalate are mixed togethersuch that the molar ratio of ethanol to dibutylphthalate is in the rangeof from about 1.5 to about 4. The blowing agent not only can provide gasfor generating foam when mixed with reactants for a foamedpolymerization reaction, but can obviate the need for a surfactant to beincluded in the reaction mix. Even when no additional surfactant isincluded, foam produced using the ethanol-dibutylphthalate blowing agentof the present invention tends to have a substantially uniform densityand be made of bubbles of substantially uniform diameter. The blowingagent can be handled safely since it has a low toxicity.

Although in general the foaming step of the process of the presentinvention need not be catalyzed, it is ordinarily preferable to do so. Acatalyst which can be used successfully to catalyze a reaction among aparticular polyhydroxy compound, a particular polyisocyanate and agas-generating agent in a conventional process to manufacturepolyurethane foam generally can also be used in the process of thepresent invention involving the same polyhydroxy compound,polyisocyanate, and gas-generating agent. Such catalysts are widelyknown in the art. Representative examples of such catalysts andpolyurethane-foam formulations in which they can be used are set forthin pages 69-75 of Vol. 21 of the Kirk-Othmer Encyclopedia cited above.As specific examples, dimethylethanol and triethylamine can be used incertain preferred formulations.

In some cases it may be desirable to adjust the pH of thebitumen-hydroxy fatty oil intermediate product in order to control therate of subsequent reactions in which the intermediate product takespart. The bitumen-hydroxy fatty oil intermediate product is typicallyacidic and can be neutralized with sodium hydroxide or other alkalinesubstance if desired.

For many applications it is advantageous to include a surfactant amongthe ingredients used to prepare the foamed polymeric material of thepresent invention, particularly when bulky castings are to be formed.Conventional silicone surfactants used in manufacturing polyurethanefoams generally function satisfactorily in the process of the presentinvention. As specific examples of preferred surfactants, the siliconesurfactants commercially available from the Dow Corning Corporationunder the trade names "Dow-Corning 193", "Dow Corning 194", and "DowCorning 197" are cited. As explained above, if theethanoldibutylphthalate blowing agent of the present invention is used,the need for surfactant is obviated.

It may also be advantageous to include a plasticizer among theingredients of the process of the present invention. Preferredplasticizers include dioctylphthalate, diisooctylphthalate,dibutylphthalate, diisobutylphthalate, dicaprylphthalate,diisodecylphthalate, tricresylphosphate, trioctylphosphate,diisooctyladipate and diisodecyladipate.

The process of the present invention can generally be carried out in thefollowing preferred manner, although it will be readily apparent tothose skilled in the art that other sequences of steps can be used. Theintermediate product is first prepared from a bitumen and a hydroxyfatty oil according to the procedure described above in an enclosedheated tank. In order to reduce air-pollution problems, the tank ispreferably connected to a water-cooled condenser to reflux and collectcondensible vapors driven off from the reactants during the heating. Theintermediate product is then cooled. At the temperature to which it iscooled, the intermediate product should be sufficiently fluid to permitmixing with other ingredients. The polyhydroxy compound and anycatalysts, surfactants and plasticizers are then thoroughly mixed withthe intermediate product. Generally from about 70 parts to about 200parts by weight of polyhydroxy compound are employed for every 100 partsby weight of the bitumen-hydroxy fatty oil intermediate product. Theresulting mixture is then combined with the polyisocyanate, blowingagent and water in a conventional mixing head for polyurethane foam.Generally a molar ratio of polyisocyanate to polyhydroxy compound in arange of from about 1:1 to about 11:1 is preferred. From about 0.5 toabout 1.75 percent by weight of water based on the weight of thepolyhydroxy compound is generally preferred. The density of theresulting foamed product is determined to a large degree by thequantities of water and blowing agent used. A temperature in the rangeof from about 30° C. to about 85° C. is preferred for carrying out thefinal mixing.

EXAMPLES

The following examples illustrate particular preferred embodiments ofthe present invention.

EXAMPLE 1

Approximately 1000 g of non-blown asphalt is placed in a stainless-steelreactor and melted by heating it to about 150° C. for about one hour.Approximately 300 g of castor oil is added to the molten asphalt and theresulting mixture is maintained at about 150° C. with stirring for aboutan hour to form an intermediate product. The intermediate product isallowed to cool to about 50° C. and the following ingredients are addedto it:

"LS 490" poly (oxypropylene) polyol--about 105 g,

"Dow-Corning 197" silicone surfactant--about 8 g,

dimethylethanolamine--about 3.6 g, and

triethylamine--about 2.0 g.

The poly (oxypropylene) polyol "LS 490" is a commercially availablepolyether polyol from Union Carbide Corporation and is believed to be areaction product of sucrose and propylene oxide catalyzed by potassiumhydroxide. This polyhydroxy compound has a hydroxyl number in the rangeof from about 350 to about 800. The resulting mixture is metered to amixing head where it is combined with water, trichlorofluoromethaneblowing agent and the polymethylene polyphenylisocyanate "PAPI". Thefour ingredients are combined proportionally in the mixing head so thatthe totals of approximately 4.15 g of water, approximately 114 g oftrichlorofluoromethane and approximately 995 g of the polyisocyanate"PAPI" are mixed with the quantities of the other ingredients listedabove. The stream of reaction mixture is discharged from the mixing headinto a mold where the foaming reaction occurs. The temperature of thereaction mixture exiting the mixing head is about 50° C. The reactionmixture is allowed to foam and cure in the mold, where it forms a tough,strong polymeric material.

EXAMPLE 2

A blowing agent is prepared by combining approximately 28.7 g of ethanoland approximately 57.7 g of dibutylphthalate. The resulting blowingagent is used in place of the trichlorofluoromethane and the siliconesurfactant of Example 1. The resulting approximately 86.4 g ofethanol-dibutylphthalate blowing agent is metered into the mixing headwhere it is mixed proportionally with the other ingredients in thequantities given in Example 1. A foamed polymeric material is producedwhich cures to a strong, tough product.

It is not intended to limit the present invention to the specificembodiments described above. For example, either blown or non-blownasphalt can be used. The foaming reactions can be either catalyzed oruncatalyzed. It is recognized that these and other changes may be madein the compositions and processes specifically described herein withoutdeparting from the scope and teachings of the instant invention, and itis intended to encompass all other embodiments, alternatives andmodifications consistent with the present invention.

I claim:
 1. A blowing agent for a polymeric foam derived from a reactionmixture comprising an organic polyisocyanate compound and a compundhaving more than one active hydrogen, the blowing agent comprising amixture of dibutylphthalate and ethanol, the molar ratio of ethanol todibutylphthalate being in the range of from about 1.5 to about
 4. 2. Amethod of preparing a polymeric foam from a reaction mixture comprisingan organic polyisocyanate compound and a compound having more than oneactive hydrogen, the method including mixing with the reaction mixturewater and a blowing agent comprising ethanol and dibutylphthalate, themolar ratio of ethanol to dibutylphthalate being in the range of fromabout 1.5 to about 4.